Theorem 2.11 ([1]}) 
Let \(K\)  be the field of fractions of the ring \({\bf C}[[x]]\)  or \({\bf C}\lbrace x \rbrace  \) . Given \(L\) , \(M\)  commuting differential operators in \(K[\partial ]\) . Let \(r\)  be the rank of the algebra \({\bf C}[L,M]\) , \(f\)  the BC polynomial of \(L\)  and \(M\)  in (REF ) and \(\Gamma \)  their spectral curve. The following statements hold:
